It's tricky — or impossible — to count Innumerous things, because there are so many of them. When you ride your bike at dusk in the summertime, right through clouds of innumerous mosquitoes, it's important to keep your mouth closed.
There are innumerous stars in the sky and innumerous grains of sand on the beach. You could also write a poem about the innumerous things you love about your girlfriend. Innumerous is primarily a literary adjective, so using it in a poem is a good idea. It comes from the Latin numerus, "a number," and the "not" prefix, in-, essentially "not able to be numbered."